Many different ultrasonic multi-plane probes, arranged for positioning within the body, have been suggested or put into actual use in the past. Depending upon the design, there are a number of shortcomings with this general class of prior art ultrasonic multi-plane probes.
Certain of these prior art ultrasonic multi-plane probes are arranged with the ultrasonic transducer array located within a cylindrical housing. Generally, these probes are larger than desired and cleaning is a problem. Although these probes are small to begin with, even smaller probes are desirable. Those engaged in the design and development of ultrasonic multi-plane probes are faced with the apparent conflicting requirements of providing as large an ultrasonic array as possible to increase resolution of the imaging and as small a housing for the ultrasonic array and other components as possible to facilitate passage of the unit through the body of a patient to the body cavity where the imaging is to be done. By containing the ultrasonic transducer array within a housing, the length and width dimensions of the housing are dependent upon the size of the ultrasonic transducer array. Also, by containing the ultrasonic transducer array within a housing, cleaning this component can be more difficult than desired.
Another problem with most of the prior art ultrasonic multi-plane probes which are arranged for positioning within the body and of which applicant is aware is the difficulty in positioning the probes in the body cavity to develop the desired high-quality images of the body organs being imaged. This problem also is due to the size of the probe. For example, in transesophageal imaging of the heart, the probe should be positioned as close as possible to and preferably in contact with the wall of the esophagus. The larger the probe, the more difficult to maneuver the probe into the desired position.
It is common practice, in the design of these probes, to fill the cavity in which the ultrasonic transducer array unit is located with a fluid and to cover the cavity with a membrane. The fluid is provided in such probes to establish the proper acoustic coupling from the array into the membrane. The very presence of the fluid in the cavity in the probe housing is the source of potential damage to the ultrasonic transducer array caused by swelling or corrosion due to the presence of the fluid in the cavity.
Yet another problem with most of the prior art ultrasonic multi-plane probes which are arranged for positioning within the body and of which applicant is aware is that the membrane cover, which is an added component in the acoustic path, can attenuate and distort sound waves in a manner which reduces ultrasound system resolution.
In addition to the foregoing, another problem with most of these prior art multi-plane probes known to applicant is that the positioning mechanism passes through seals which are susceptible to leakage of body fluids into the probe cavity to contaminate the fluid in the probe cavity possibly leading to corrosion and acoustic problems. Leakage of the probe cavity fluid into the patient also can occur, but this problem is overcome by using biocompatible fluid in the probe cavity.